1. Field of the Invention
The present invention relates to a three dimensional (3D) image display system, and in particular relates to a naked-eye type 3D image display system, an image display device, and electronically switchable light modulating cells thereof.
2. Description of the Related Art
In Nature 425, 383 (2003), Hayes et al. discloses a novel on/off switch method, which applies electrowetting principle to control colored oils. This technology had several advantages such as high color saturation, high image response speed, and low energy consumption, as compared to conventional technologies. Therefore, electrowetting was soon applied in display technology field.
In Applied Physics Letters 85, page 1128 (2004), S. Kuiper et al. published a paper titled “Variable-Focus Liquid Lens for Miniature Cameras” that described an optical lens, where an input voltage is used to tune a curvature ratio of an interface between two incompatible fluids. By changing the input voltage, a variable-focus liquid lens for miniature cameras is achieved.
In related arts, liquid lenses made of mini-scaled capillary array devices are manufactured by micro-electro-mechanical system (MEMS) processes. The capillary surface may be an interface between a gas and a liquid or between two liquids, and the shape of the interface is determined by surface tension of the liquids. In Applied Physics Letters 87, pp. 134102(2005), Hirsa et al. published a paper titled “Electrochemically Activated Adaptive Liquid Lens”, where a reversible capillary switch having low energy consumption is formed on a single chip. The capillary switch scaling from mini meters to micro meters is arranged in a single mode or in an array mode. The capillary switch that controls a droplet interface shape has been applied in near and far field optics, data access systems, near field lithography systems, microscopy, and surface shape manufacturing systems.
Displays capable of showing stereoscopic images or animations are called three-dimensional (3D) image displays. Major developments in the 3D display fields have led to two types of technologies: a polarized glasses type and a naked-eye type. Meanwhile, 3D display effects may also be theoretically accomplished by using holography. However, holography needs interference of several light beams to display 3D images.
Because the naked eye type 3D display only utilizes a light beam control element in front of a display, it is relatively easy to display 3D images, as compared to the holography. The light beam control element is generally a barrier layer or a lenticular lens that controls or changes deflection angles of light beams. As such, right eye images are deflected to a right eye of a viewer, and left eye images are deflected to a left eye of the viewer, respectively.
In U.S. Pat. No. 6,275,254 (titled “AUTO-STEROSCOPIC DISPLAY DEVICE AND SYSTEM”) discloses a 3D image display, which solves the problem of narrow view zones. A planar cathode tube radiation (CRT) display is collocated with a specific magnetic element on parts of vertical pixels of the CRT display to deflect electron beams, thereby controlling the pixels. Moreover, the other parts of the vertical pixels are collocated with lenticular lens screens. Although a multi-view display is achieved, a specific planar CRT is required.
U.S. Patent Publication No. 2010/0214634 (titled “Holographic Reconstruction System with an Optical Wave Tracking Means”) describes a holographic reconstruction system which comprises a spatial light modulator, a light source, light-controlling cells, an eye finder, and a system controller (SC). The eye finder may search an eye position of a viewer, locate the eye position, and then transmit the location information back to the system controller. Thereafter, the system tunes an applied voltage to control the emitting direction of light beams from the light-controlling optic cells to display 3D images for a moving viewer. The light-controlling cells may be a control unit based on the electrowetting theory. However, the holographic reconstruction system which utilizes interference or holography images is not a lenticular lenses-based system that separates light beams into right eye light beams and left eye light beams to display 3D images.
U.S. Patent Publication No. 2010/0225986 (titled “Display Device with an Active Matrix of Electrowetting Cells”) describes a display device driven by an active matrix, which includes at least one data driver circuit and at least one selection driver circuit. The active matrix is electrically connected to the at least one data driver circuit and the at least one selection driver circuit, and electrowetting cells are directly driven by the active matrix. However, the active matrix shields light beams and thus reduce the aperture ratio of the display device.
U.S. Pat. No. 6,369,954 (titled “LENS WITH VARIABLE FOCUS”) discloses variable-focus lenses. As shown in FIG. 1, the variable-focus lenses includes a chamber 12 filled by a first liquid 13 and a second liquid 11 which contacts with a surface 15, and has an appearance of a droplet. The first liquid 13 and the second liquid 11 are transparent and incompatible, and have different refractive indexes. An electrode 16, plated on an outer surface of the chamber 12, surrounds the contact surface 15. The electrode 16 connects to an electrode 17, which contacts the first liquid 13. The first liquid 13 and the second liquid 11 have different properties with respect to electrowetting, such that the curvature ratio of the interface between the first liquid 13 and the second liquid 11 is changed by applying a voltage. FIG. 1 shows a change from a curvature ratio A to a curvature ratio B. It is noted that by changing the interface curvature ratio, the focal length of the lenses may be tuned without tuning other factors of the lenses.
U.S. Pat. No. 7,688,509 (titled “AUTOSTEREOSCOPIC DISPLAY”) discloses that liquid lenses are collocated with splitting screens to display 3D images. As shown in FIGS. 2A and 2B, the electrodes in an electrowetting cell include side electrodes and a bottom electrode, and fluids in the electrowetting cell include incompatible oil 73 and water 74. The electrowetting lens 71 is operable by applying different voltages to the side electrodes and the bottom electrode, such that a curvature ratio of the interference of the two incompatible fluids is tuned to modulate the emission directions of light beams traveling therethrough. As shown in FIGS. 2A and 2B, the electrowetting lens 72 is another device, which tunes the emission direction of light beams traveling therethrough. Different voltages are applied to the left and right side electrodes and the bottom electrode to tune an inclined angle of the interface of the incompatible fluids, thereby modulating the emission direction of the light beams traveling therethrough.
In U.S. Patent Publication No. 2009/0257111, a tunable optical array device includes a substrate on which a TFT tuning circuitry is disposed for controlling an upper layered cell array. Two incompatible fluids having different polarities are filled in cells of the cell array, and the shape of the interface between the fluids is controlled by lower layered TFT tuning circuitry. Accordingly, phase modulation and beam deflection of light beams traveling through the cell array can be controlled. Also disclosed are driving methods of the TFT tuning circuitry. However, using a TFT driving mechanism may dramatically reduce the aperture ratio of the display. While an interconnect layer is also disclosed, the brightness of the display is reduced by the multi-layered structure of the interconnect layer.
In U.S. Patent Publication No. 2009/0257111, an electrowetting display having multiple cells is applied in a holographic reconstruction system. Interference fringes of light beams are generated through the electrowetting cells. The electrowetting display may deflect the light beams traveling therethrough to the eyes of a viewer. Although the electrowetting display may deflect light beams, it lacks the concept of time-multiplexing. The electrowetting device can be applied in retro-reflective panels, image projection devices, and holographic projection reconstructing equipments.
In U.S. Patent Publication No. 2010/0157026 (titled “DIRECTIONAL ILLUMINATION UNIT FOR AUTOSTEREOSCOPIC DISPLAYS”), a 3D image display includes a light emitting device, an image device, a light beam deflection device, an image display device, a viewer tracker, and an image control circuit. The light emitting device can be a surface emitting diode or a backlight. The image display device can be a spherical mirror, an aspherical mirror, a holographic optical element, or an interference optical element. The light beam deflection device can be electrowetting elements. The image display device has pixel structures, which can be simultaneously modulated to display a discrete different image series. As such, a viewer may view 2D or 3D images. The viewer tracker includes a detection mechanism which detects viewer position. The light emitting device emits light beams which travel through the image device as parallel light beams, holographic images, or optical interference images. The parallel light beams or the like deflected by the light beam deflection device would travel to the image display device for simultaneously modulating separate image arrays. The system does not process images by persistence of vision, and it does not process separate image arrays. Also, the optical path design of the system is relatively complicated.
Therefore, a novel 3D image display is desirable, which simultaneously modulate focal length and emission light beam direction of relatively large display areas.